The overall objective of the present proposal is to explore the role of kinins in mesangial cell proliferation and to characterize the kinin signaling pathways involved in mediating these events. Increasing evidence indicates that mesangial cell proliferation is important in the pathogenesis of mesangial expansion; mesangial cell hypertrophy, hyperplasia and matrix accumulation may ultimately lead to glomerulosclerosis. The signals which initiate proliferation are not clearly defined although a number of mediators have been implicated. We have accumulated evidence that the renal kallikrein-kinin system mediates the renal hemodynamic changes induced by diabetes and dietary protein. A role for renal kallikrein and kinins as growth factors for mesangial cell expansion has not been explored. Our recent preliminary data, indicate for the first time, that kinins directly increase DNA synthesis, induce oncogene expression and MAP-kinase activation in vascular smooth muscle cells, and stimulate tyrosyl phosphorylation of cytoplasmic and nuclear proteins in mesangial cells. Therefore, we propose to investigate the role of kinins in mesangial cell proliferation and to dissect the intracellular pathways by which kinins propagate their effects from the cell surface to the nucleus. We will: Test the hypothesis that kinins promote proliferation of glomerular mesangial cells. To do this we will determine if kinins induce mesangial cell hypertrophy and/or hyperplasia by assessing the influence of kinins on protein and DNA synthesis, cell viability and cell number. We will evaluate whether endogenous generation of nitric oxide or eicosanoids in mesangial cells modulate the growth promoting effects of kinins. Identify the early response proto-oncogenes (c-myc, c-jun, c-fos) that may be induced in response to kinin challenge. Evaluate whether transcriptional activation of the activator protein (AP- 1) complex contributes to nuclear signaling by kinins. To characterize the signaling pathway(s) that link kinin-receptor interactions to stimulation of mesangial cell growth. We will identify cytoplasmic and nuclear proteins that may be phosphorylated in response to kinin stimulation. Specifically, we will study the phosphorylation of pp/60c- src, tubulin, MAP-kinase and c-Jun. Determine whether MAP-kinase is activated in response to kinin and if so, whether MAP-kinase translocates from the cytoplasm to the nucleus.